One vertex per element, one color per generator, with an edge from x to x·s.
(9,10)(11,15)(12,19)(13,14)(16,20)(17,21)(18,24)(22,23)(25,26,30,28)(27,33,35,31)(29,36,38,32)(34,39,37,40)(1,2)(3,4)(5,7)(6,8)(11,17)(15,21)(18,23)(22,24)(26,28)(31,33)(32,36)(39,40) involution — undirected(1,3)(2,6)(4,7)(5,8)(10,14)(15,21)(16,19)(22,24)(25,27,30,35)(26,31,28,33)(29,37,38,34)(32,40,36,39)(1,4,5,6)(2,3,7,8)(9,10)(11,15)(12,16)(13,14)(17,21)(18,22)(19,20)(23,24)(25,27)(26,31)(28,33)(29,34)(30,35)(32,39)(36,40)(37,38)(1,4)(2,3)(5,6)(7,8)(9,11)(10,15)(12,18)(13,17)(14,21)(16,22)(19,24)(20,23)(25,28,30,26)(27,31,35,33)(29,36,38,32)(34,39,37,40)(1,2)(3,4)(5,7)(6,8)(9,12)(10,16)(11,18)(13,20)(14,19)(15,22)(17,23)(21,24)(25,29,30,38)(26,32,28,36)(27,34,35,37)(31,39,33,40)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.